Image broken when render in Video Sequence Editor mode
Speculating as we don't have enough information here to be conclusive, but this looks suspiciously like an issue with I / B / P frames.

Specifically, your in point on a sequence with B frames may not have enough information to fully build the frame as the decoder would need to decode both the previous I frame, but also the following I frame. If you have trimmed the strip to be in the middle of those I frames, you don't have enough information and you end up with that half broken frame.

Best advice, as usual, is to never use codecs for editing. Render to an intermediate frame sequence and use those as your footage inputs. This will also increase the quality of the work.